Leggy Fence Lizards Show Rapid Evolution

The world is a rapidly changing place these days, and one strategy to deal with change is to evolve. In the southeastern United States our native fence lizards are evolving… into a fitter species. It took Charles Darwin over 20 years to complete ‘on the origin of species’ and even then only because Wallace was poking about with similar ideas. Yet it has only taken the fence lizards 68 years (38 generations) to evolve new behaviors and longer hind legs. What has caused this rapid evolution of long legged lizards?

Fence lizard relaxing in the sun photo: Tracy Langkilde

Penn State Assistant Professor Tracy Langkilde found that Darwin isn’t the only one who has to put up with others poking about in their territory. In the 1930s the fence lizards suddenly had a new neighbor, the invasive fire ants from South America.

"Fire ants need protein, especially for their developing brood," said Langkilde. "It takes just 12 of them less than a minute to kill a three-inch-long fence lizard. In fact, they have even been known to eat animals as large as calves, stripping them down to their bones."

Fire ants on centepede photo: Tracy Langkilde

The formidable fire ants present a life or death situation to the fence lizards, and those lizards with longer legs and fancy moves are able to escape the ants, while their more stubby cousins allow them to pass on their genes.

"The lizards can survive this attack by twitching to flick off the ants and then by running away from the mound," said Langkilde who filmed a video of this twitch and run behavior. "We found that the lizards from sites that have been invaded the longest were more likely than the lizards from sites that have not yet been invaded to perform this survival behavior. Many of the lizards from the uninvaded site and the most recently invaded site just sat there with their eyes closed while the ants attacked," said Langkilde.

Climate change, land use, and transportation patterns are transforming our world. The introduction of species, or their changing migration patterns and habitat can cause extinction or in cases like the fence lizard - rapid evolution.

"Not only does this finding provide biologists with an example of evolution in action, but it also provides wildlife managers with knowledge that they can use to develop plans for managing invasive species," said Langkilde.